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December 5, 2019

How do you protect a tunnel where boulders fly through it at 50 mph? You line it with granite

  • Engineers say relining the tunnel at Mud Mountain Dam near Enumclaw with granite blocks will cost less to maintain.
    Special to the Journal

    Photos courtesy of Garney Construction [enlarge]
    Garney Construction placed 2,000 granite blocks, weighing 1,350 pounds each, in the tunnel’s floor at Mud Mountain Dam. The tunnel is pummeled by boulders as large as 2 feet in diameter.

    An inlet ramp builds up to the granite blocks.

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